Five major banks, including UBS, "agreed to plead guilty to U.S. felony charges for rigging foreign currency exchange rates and pay a total of nearly $5.7 billion in fines" in May 2015, according to the L.A. Times. The banks agreed to the fines and three years of "corporate probation" with federal supervision and regular reporting requirements as part of a settlement agreement with U.S. and European officials.[1] Somewhat unusually, it was the banks' parent companies that entered guilty pleas, not subsidiaries.[2]

Traders at Citicorp, JP Morgan Chase, Barclays, the Royal Bank of Scotland, who reportedly referred to themselves as "The Cartel," were accused of manipulating currency prices between December 2007 and January 2013. The banks "each agreed to plead guilty to one felony count of conspiring to fix prices and rig bids for foreign currency exchange," the L.A. Times reported.[1]

The fifth bank, UBS, was found to have violated an earlier agreement made in 2012 after a Justice Department investigation into manipulation of Libor, a key global interest rate.[1]

Prosecutors said that traders "colluded to pad their returns from at least 2007 and 2013. To carry out the scheme, one trader would typically build a huge position in a currency, then unload it at a crucial moment, hoping to move prices. Traders at the other banks would play along, coordinating their actions in online chat rooms."[2]

The New York Times described the case as

"paint[ing] the portrait of something more systemic: a Wall Street culture that enabled many big banks to break the law even after years of regulatory black marks after the crisis.

“If you aint cheating, you aint trying,” one trader at Barclays wrote in an online chat room where prosecutors say the price-fixing scheme was hatched."[2]

Barclays: $550 million, plus a $60 million criminal penalty for violating an earlier agreement related to a Libor manipulation investigation in 2012, and $1.3 billion in settlements to the Commodity Futures Trading Commission, the New York State Department of Financial Services and the United Kingdom’s Financial Conduct Authority

JP Morgan Chase: $550 million

Royal Bank of Scotland: $395 million

UBS $203 million, for violating a 2012 Libor investigation agreement. UBS also pled guilty to one count of wire fraud.

In addition, the Federal Reserve announced that it would impose $1.6 billion in fines on the banks.[1]